The present invention relates in general to a locking arrangement for flexible, annular covers and in particular, to locking members formed integral with a cutting mat for securing to a rotary anvil.
Rotary die cutting machines are used to cut a continuously moving workpiece by passing the workpiece through the nip of a cutting roller and a rotary anvil. The cutting roller includes any combination of cutting blades or rules, and scoring elements projecting from the surface thereof. The rotary anvil provides a suitable surface to support the workpiece at the point where the work material is cut or scored by the cutting roller. Essentially, the rotary anvil serves as a backstop allowing the cutting blades to be urged against the workpiece being cut without damaging the cutting blades themselves. Because of the speed of operation, rotary die cutting machines are used to perform cutting operations in numerous industries. For example, the corrugated industry utilizes such machines to cut and score corrugated paperboard materials for constructing packaging products such as boxes and shipping containers.
Typically, several cutting mats are axially aligned on the rotary anvil. Each cutting mat is constructed of a deformable material such as a polymeric composition. The outer surface of each cutting mat is sufficiently rigid to give adequate support to the work material, yet soft enough so that the cutting blades will not wear or be damaged by impact with the rotary anvil. The cutting blades on the cutting roller penetrate the cutting mats in operation. This leads to eventual fatigue and wear of the cutting mats, requiring periodic replacement.
At times, rotary die cutting machines are set up to feed a workpiece centrally, and as such, the full width of the rotary die cutting machine is not used. Under this circumstance, the cutting mats located generally in the central portion of the rotary anvil experience most of the wear. Likewise, the cutting mats located at the opposing end portions of the rotary anvil receive the least wear. Rotating the relative positions of the cutting mats on the rotary anvil such that the cutting mats wear more evenly may prolong the serviceable life of cutting mats. However, repositioning the cutting mats causes downtime because the rotary die cutting machine cannot be in operation when changing or adjusting the cutting mats. The number of cutting mats on a typical rotary anvil can range from eight to fourteen mats, thus the downtime can become substantial. Further, as the cutting mats wear, the quality of the cutting operation deteriorates. However, because of downtime, the industry tendency is to prolong the time between cutting mat changeovers. This leads to a greater possibility of poor quality cuts.
Several techniques have been devised to secure the cutting mat to the rotary anvil. For example, several known cutting mats include opposing flanged end portions that are received in a lock up channel axially extending along the surface of the rotary anvil. However, the flanged portions of such cutting mats are formed either by welding a frame to the end portions of the cutting mat to define the respective flanges, or otherwise adhering a metal liner to the interior surface of the cutting mat, then bending numerous folds into the liner until the liner defines the framed flange. Such approaches are costly and complicate the manufacturing process. Further, a seam is created where the ends of the cutting mat meet in the axial channel. Should a cutting blade strike the cutting mat along that seam, the cutting blade can slip between the end portions of the cutting mat potentially damaging the cutting blade.
Still other lockup devices comprise complimentary interlocking fingers cut into opposing ends of the cutting mat. Such devices attempt to eliminate the use of flanged end portions of a cutting mat. For example, one cutting mat construction comprises opposite ends having a plurality of complimentary fingers and receivers. The cutting mat is wrapped around the rotary anvil, and the ends are joined in puzzle like fashion. However, this construction may not provide suitable holding strength and the cutting mat may slip. Further, the ends of the cutting mat may pull away or slightly lift from engagement with each other causing one or more ridges or humps to be formed on the outer surface of the cutting mat. These ridges may interfere with the smooth operation of the rollers and as such, are detrimental to the rotary die cutting procedure. Cutting mats that incorporate interlocking fingers can also be difficult to install and mount leading to increased downtime, and infrequent cutting mat changeover.
The present invention overcomes the disadvantages of previously known locking systems for cutting mats by providing a lockup device that allows for rapid cutting mat changeover, and installation. The cutting mat comprises a cutting mat body and a lock assembly arranged to secure the cutting mat to a rotary anvil. The lock assembly comprises male and female locking members positioned at opposite ends of the cutting mat and formed integral therewith. The female locking member slips into an axial channel on a rotary anvil. The cutting mat is wrapped around the rotary anvil, and the male member is inserted into the axial channel in locking relationship with the female locking member. The female and male locking members are constructed of the same material as the remainder of the cutting mat and formed integral therewith resulting in a one-piece construction that enables rapid cutting mat changeover. Rapid cutting mat changeover is realized because there are no bolts, latching strips, glue or additional components such as lockup devices required for installation. Additionally, the cutting mat is non-directional when placed on a rotary anvil.
To prevent a cutting blade from slipping between the male and female locking members during cutting operations, the opposing axial edges of the cutting mat are formed in a complimentary nonlinear pattern. For example, the axial edges of the cutting mat are formed in a mating serpentine shape. As such, the axial seam defined between the female and male locking members is not linear as taken across the entire width of the cutting mat ensuring that a cutting blade will always strike at least a portion of the cutting mat surface. Further, the serpentine shaped joint or seam allows for better alignment of adjacent cutting mats.
Accordingly, it is an object of the present invention to provide a cutting mat having complimentary, nonlinear axial edges arranged such that when the cutting mat is installed on a rotary anvil, the axial edges mate together to define a nonlinear seam arranged to prevent a cutting blade from slipping through the seam.
It is another object of the present invention to provide a cutting mat having female and male locking members formed integral with the cutting mat.
It is an object of the present invention to provide a cutting mat that secures to the cylinder portion of a rotary anvil using frictional forces only.
It is still another object of the present invention to provide a cutting mat having a lock assembly that allows for quick cutting mat changeover and replacement without disturbing adjacent cutting mats.
Other features of the present invention will become apparent in light of the description of the invention embodied herein, the accompanying drawings, and the appended claims.